The Children's Cancer Study Group is a multi-disciplinary organization formed to cooperate in research into malignant diseases in children: specifically, to study the factors which may cause or influence these diseases, and to develop, evaluate and improve methods of treatment. The primary objective of the cooperative group has been to evaluate new biological and chemotherapeutic agents in the treatment of acute leukemia and solid tumors in childhood, and find new and better ways of using the already known agents. This evaluation is done by pediatric oncologists, surgeons, radiotherapists, pathologists and immunologists within the cooperating institutions which make up the group. It is also our objective to provide supportive care for these children with leukemia and solid tumors which will enable all children who desire to do so to participate in our protocol studies. This supportive care includes financial supportive care (domiciliary care, travel assistance, outpatient costs, etc.), social service assistance, as well as medical supportive care.